The invention concerns conveyors which include means for reorienting and respacing the articles being conveyed. More particularly, it concerns a collating conveyor arrangement suitable for handling relatively flat, generally rectangular, filled and closed flexible walled bags, and which receives the bags spaced apart and lying flat and delivers them in a collated upright column.
A collating operation is commonly used in preparing bagged product for shipment. Typically, the bags are received from an automatic bagging machine, conveyed spaced apart and lying flat in edge-to-edge relationship. Collation brings the bags together, generally upright in a horizontally extending column, so that successive, multiple-bag portions of the column may be conveniently handled and placed in a shipping container.
The labor cost of manual collation is relatively high and, if the product is fragile, there is a risk of damage from operator error or carelessness. Collation of bagged products which are not easily damaged, and hence able to stand some pressure in the process, is readily mechanized as shown, for example, in Harker U.S. Pat. No. 2,941,676. The collated column may be assembled in a delivery chute as in Harker, or on a takeoff conveyor (preferably intermittently driven) as disclosed by Mosterd U.S. Pat. No. 3,590,972. The chute arrangement, exemplified by Harker, is suitable for bagged product which can tolerate some deformation and pressure. Maintenance of the collated arrangement depends on friction between the bags and the sides of the chute and the collated column is advanced along the chute only by the pressure of the platen as it adds another bag to the column. Salomon U.S. Pat. No. 3,445,980 also uses a "pushed" column in a chute (for tea bags), but here feeding pressure is applied to the column through the camming action of the "wings" of a star wheel feeder rather than by a platen. When a takeoff or delivery conveyor is used, as in Mosterd, the collated product is handled more gently. However, Mosterd is designed especially for handling objects, such as egg trays, where an inversion operation is required before the handling of bagged product.
Fallas U.S. Pat. No. 4,356,906 recognizes some features desirable in a collating conveyor for handling more delicate bagged products, such as potato chips in plastic or waxed paper bags. The system should cope with the irregular arrival of bags at the collating station; any erecting device must be gentle; in the collated column, the bags must be together but not crushed; and the erecting device must not interfere with or damage oncoming bags, especially if they arrive while the preceding bag is being erected or reoriented. In Fallas, the feed and takeoff conveyors are in approximately the same horizontal plane (actually the takeoff conveyor is somewhat elevated) and longitudinally aligned. The collating mechanism includes a generally horizontal erecting table which connects the conveyor portions and slidingly supports each bag while a "flipper" or erector arm lifts it upright, through an angle in excess of 90.degree., while moving it to the downstream end of the table adjacent the takeoff conveyor. From there it is pushed onto the takeoff conveyor either directly by the flipper or by the arrival of the next bag. Fallas finds it necessary to use a four-bar linkage and approximately 135.degree. of rotation of his drive mechanism to carry his flipper from its approximately horizontal attitude, emerging from the collating unit table at its upstream end, to its upright and upwardly extending position towards the downstream end, followed by a further 225.degree. of rotation to retract the erector beneath the surface of the table into position ready for the next cycle, all of which requires an excessively long cycle time.
Sensed arrival of a bag at the upstream end of the Fallas collating table actuates the flipper for one cycle. Intermittent drive of the takeoff conveyor is synchronized with the flipper action by virtue of being driven by the flipper mechanism so that the takeoff conveyor belt is advanced or indexed during the flipper action rather than after the action is completed. Accordingly Fallas provides no "backup" to guard against bags in the column falling backwards due to acceleration at the start of indexing.
Fallas provides means for adjusting the distance advanced or indexed by the takeoff conveyor for each collating cycle, but during operation this distance is fixed. Improper takeoff conveyor stroke adjustment or variation in thickness or shape of the bags may therefore result in poorly collated columns which are irregular because of crowding (with potential damage to the product) or unevenly or extensively spaced. Accordingly, Fallas suggests an alternative in which "the stroke of the ratchet assembly (driving the takeoff conveyor) might be made to be adjustable during operation of the machine". However this would require monitoring and careful adjustment. The problem of both Fallas and Mosterd in this regard is that they rely on upstream detection to signal actuation of the takeoff conveyor (and the collating erector mechanism in Fallas). There is no feedback of the actual position or condition of the existing collated column on the takeoff conveyor to control its actuation.